The invention finds utility in the field of Cable Modem Termination Systems (hereafter CMTS).
In the early stages of broadband cable modem deployment, frequently individual neighborhoods served by a cable systems do not have a full complement of customers. Today, CMTS receivers are available that have the capability to handle a constant stream of bursts at 5.12 megasymbols per second. Such CMTS receivers are available from the assignee of the invention. If such a receiver is dedicated to serving one cable system coupled to the homes in one neighborhood, it will be underutilized during the initial stages of deployment because not enough bursts are being transmitted upstream from the served neighborhood to keep the CMTS receiver busy full time. This problem would exist if a single CMTS receiver is dedicated to each cable in a CMTS which is coupled to multiple cable systems.
The solution to this problem which has been attempted in the prior art is to concentrate all the bursts from all the cable systems serving multiple different neighborhoods together on one cable. This creates an even bigger noise problem than the cable upstream of a single cable system already has because all the noise from all the cables is concentrated into one cable that is coupled to the CMTS receiver. This, therefore, is an unsatisfactory solution since noise in the upstream is already a well recognized problem even in a single cable system. To multiply this noise problem by aggregating bursts from multiple cable systems into one cable is untenable.
Further, the assignee of the present invention has developed a technology to decouple downstreams from upstreams. This allows flexible mapping of upstreams to downstreams which can be controlled from the CMTS. Further, with this technology, more than one upstream can share a single downstream and more than one downstream can share a single upstream. The ability to do this has created a need for a line card which has only one or more upstream receivers thereon as opposed to the fixed ratio of upstream receivers and downstream transmitters found in prior art line cards. With prior art line cards, as the cable operator encounters the need to add more upstream capacity as penetration becomes larger, the cable operator is forced to buy downstream transmitter capacity simultaneously which he does not need. Therefore a need has arisen for an upstream line card which only has upstream receivers on it and no downstream transmitters to allow more flexibility in adding upstream capacity without having to simultaneously add unneeded downstream capacity.